Consumer electronics with flip covers, such as portable computer, electronic dictionary, portable audio/video player, flip mobile phone, generally have a main body on the bottom, which is pivotally connected with the cover to body on the top, such that the cover body may swing open or close with respect to the main body. Consequently, the rotating axle is key to the quality of the products described above.
To prevent the main body and the cover of the 3C electronic products described above from swinging open arbitrarily, at least a sliding or pressing switch is provided at the respective limit of the movement angle such that the switch may be used to fold them together to close down during swinging close. However for this type of automatic locking mechanism, the rotating shaft structure with automatic locking mechanism has to be provided with corresponding holes and locking elements, leading to an increase in the complexity for assembly and the manufacturing cost. It is therefore necessary to provide a new design to overcome the drawbacks described above.
Consequently, to provide the cover body with an auto-locking function with respect to the main body, it is a conventional approach to dispose a cam member in the hinge structure, such that the protruded portion of a rotation member of the cam member is engaged into an indented portion to mate together and thus to achieve the desired auto-locking function. Therefore, when the cover is being flipped open through the cam member, a user has to provide a force to render the protruded portion to move out the indented portion, thereby achieving a hinge structure with the “easy opening and firm closing” function. It is not a user-friendly design because a rather large force has to be exerted to flip open the cover body. As a result, the flipping opening motion usually requires the user to press down the main body with the other hand; otherwise, the main body will be lift upward along with the cover body, thereby causing inconvenience. Therefore it is an urgent task to provide a variable torque mechanism with “easy opening and firm closing” characteristic when the cover body is being opening up with respective to the main body.